It is known that the inside surface of a contact lens, i.e., the surface which lies on the cornea, must be aspherical, more specifically, elliptical, in order to adapt to the surface of the human cornea ("The Contact Lens", 9th year of publication, Volume 3, 1974, pages 211 to 217).
Despite intensive research, a soft contact lens has still not been developed with a single internal geometry suitable for the majority of wearers, i.e., fitting a substantial range of corneal sizes, within a relatively wide vertex refractive range.